In large aperture phased array antennas, performance requirements such as high array gain and low slidelobe levels often preclude the use of thinning or increased element spacing to reduce element count. As a result, very large numbers of active elements are required; e.g., approximately 10,000 elements for a 1 degree beamwidth array operating at 10 GHz. Typically, each antenna element in the array includes a printed circuit microwave phase shifter which varies the phase of the signal input thereto. Such phase shifters comprise a microwave printed circuit etched on an alumina substrate, with conventional PIN diodes mounted to the circuit to provide the phase shift. The output of this circuit is typically connected to a radiating dipole element via an RF connector and length of semi-rigid RF cable.
In a phase shifter-per-element configuration, the phase shifter often becomes a major contributor to both the cost and weight of the phased array, as well as contributing significantly to the RF loss. Therefore, although conventional PIN diode phase shifter configurations provide reasonably efficient performance, there is a need to reduce phase shifter cost, weight and RF loss in phased array antenna design.